WO2015121584A2

WO2015121584A2 - Method of manufacturing a fibrous material preimpregnated with thermoplastic polymer using an aqueous dispersion of polymer

Info

Publication number: WO2015121584A2
Application number: PCT/FR2015/050332
Authority: WO
Inventors: Patrice Gaillard; Gilles Hochstetter; Thibaut SAVART
Original assignee: Arkema France
Priority date: 2014-02-13
Filing date: 2015-02-11
Publication date: 2015-08-20
Also published as: EP3105026A2; FR3017330A1; FR3017330B1; CN106163776B; ES2793943T3; KR20160110446A; EP3105026B1; US20160347009A1; JP2017505853A; KR101909363B1; JP6495932B2; WO2015121584A3; CN106163776A

Abstract

The invention relates to a method of manufacturing a preimpregnated fibrous material comprising a fibrous material of continuous fibres and a thermoplastic polymer matrix, characterized in that said preimpregnated fibrous material is produced as a unidirectional single tape or a plurality of unidirectional parallel tapes and in that said method comprises the following steps: i) a step of impregnating said fibrous material while it is in the form of several parallel rovings, said impregnation step comprising: ia) immersing said fibrous material in a bath containing an aqueous dispersion (22) of said thermoplastic polymer, said immersion being followed by ib) a drying (25) of said fibrous material, then ii) a step of shaping said parallel rovings of said fibrous material impregnated according to step i) by calendering using at least one heated calender (51, 52, 53) into the form of a plurality of unidirectional parallel tapes using said heated calender comprising a plurality of calendering grooves (73), preferably up to 200 calendering grooves, according to the number of said tapes and with a pressure and/or separation between the rolls (71, 75) of said calender regulated by a control system.

Description

METHOD FOR MANUFACTURING THERMOPLASTIC POLYMER PRE-IMPREGNATED FIBROUS MATERIAL USING AQUEOUS DISPERSION

POLYMER

[Field of the invention!

The present invention relates to a method of manufacturing a fibrous material pre-impregnated with thermoplastic polymer.

More particularly, the invention relates to a method of manufacturing a preimpregnated fibrous material comprising an impregnation step followed by a shaping step for obtaining ribbons of fibrous material pre- impregnated, of calibrated dimensions, directly usable for the manufacture of three-dimensional composite parts.

In the present description, the term "fibrous material" means an assembly of reinforcing fibers. Before it is shaped, it is in the form of wicks. After shaping, it comes in the form of strips, or tablecloths, or pieces. When the reinforcing fibers are continuous, their assembly constitutes a fabric. When the fibers are short, their assembly constitutes a felt or a nonwoven.

The fibers that can be used in the composition of the fibrous material are more particularly carbon fibers, glass fibers, basalt fibers, silicon carbide fibers, polymer-based fibers, vegetable fibers, or cellulosic fibers used alone or as a mixture.

Such preimpregnated fibrous materials are particularly intended for the production of lightweight composite materials for the manufacture of mechanical parts having a three-dimensional structure and having properties of good mechanical strength, thermal and capable of discharging electrostatic charges. , that is to say properties compatible with the manufacture of parts in particular in the fields of mechanics, aeronautics and nautical, automotive, energy, health and medical, army and armaments, sports and recreation, and electronics.

Such preimpregnated fibrous materials are also called composite materials. They comprise the fibrous material, constituted by the reinforcing fibers, and a matrix constituted by the impregnating polymer. The primary role of this matrix is to maintain the reinforcing fibers in a compact form and to give the desired shape to the final product. Such a matrix serves inter alia to protect the reinforcing fibers against abrasion and an aggressive environment, to control the surface appearance and to disperse any fillers between the fibers. The role of this matrix is important for the long-term behavior of the composite material, particularly with regard to fatigue and creep.

[Prior art]

A good quality of the three-dimensional composite parts manufactured from preimpregnated fibrous materials therefore passes through a control on the one hand of the impregnating process of the reinforcing fibers by the thermoplastic polymer and on the other hand the process of shaping the preimpregnated fibrous material as a semi-finished product.

In this description, the term "band" is used to designate strips of fibrous material whose width is greater than or equal to 100mm. The term "ribbon" is used to designate ribbons of calibrated width and less than or equal to 100 mm.

Until now, the manufacture of fibrous material webs reinforced by impregnation of thermoplastic polymer or thermosetting polymer was carried out according to several processes which depend in particular on the nature of the polymer, the type of final composite material desired and its field of applications. Powder deposition or extrusion technologies of molten polymer are used to impregnate the reinforcing fibers with thermosetting polymers, such as epoxy resins for example, as described in the patent WO2012 / 066241 A2. These technologies are not generally applicable directly to the impregnation with thermoplastic polymers, in particular those with a high melting temperature, which have a melt viscosity that is too high to obtain satisfactory impregnation of the fibers and semi-finished products or finished of good quality.

Companies market strips of fibrous materials obtained by a method of impregnating unidirectional fibers by passing the fibers continuously in a melt of thermoplastic polymer containing an organic solvent such as benzophenone. For example, US Pat. No. 4,541,884 of Imperial Chemical Industries can be referred to. The presence of the organic solvent makes it possible in particular to adapt the viscosity of the molten mixture and to ensure good fiber coating. The fibers thus pre-impregnated are then shaped. They may for example be cut into strips of different widths and then placed under a press, then heated to a temperature above the melting temperature of the polymer to ensure the cohesion of the material and in particular the adhesion of the polymer to the fibers. This method of impregnation and shaping makes it possible to produce structural parts with high mechanical strength.

[001 1] One of the disadvantages of this technique lies in the heating temperature required to obtain these materials. The melting temperature of the polymers depends in particular on their chemical nature. It can be relatively high for poly (methyl methacrylate) (PMMA) polymers, or even very high for poly (phenylene sulfide) (PPS), poly (ether ether ketone) (PEEK) or poly ( ether ketone ketone) (PEKK) for example. The heating temperature can therefore rise to temperatures higher than 250 ° C., and even higher than 350 ° C., temperatures which are much higher than the boiling point and the flash point of the solvent, which are respectively 305 ° C. and 150 ° C for benzophenone. In this case, there is a sudden departure of the solvent inducing a high porosity within the fibers and therefore causing the appearance of defects in the composite material. The process is therefore difficult to reproduce and involves risks of explosion endangering the operators. Finally, the use of organic solvents is to be avoided for environmental and health and safety reasons.

EP 0 406 067, filed in the joint names of Atochem and the French State, as well as document ΕΡ0 201 367 describe a technique for impregnating a fluidized bed of polymer powder. The fibers enter a closed fluidization tank where they are optionally separated from each other by means of rollers or corrugated rolls, the fibers being electrostatically charged by friction in contact with these rollers or rolls. This electrostatic charge allows the polymer powder to stick to the surface of the fibers and thus to impregnate them.

Another known method of impregnation is the continuous passage of the fibers in an aqueous dispersion of polymeric powder. . For example, reference can be made to EP0324680. In this process, a dispersion of powders of micrometric size (about 20 μηη). After soaking in the aqueous solution, the fibers are impregnated with the polymeric powder. The process then involves a drying step of passing the impregnated fibers through a first furnace to evaporate the water absorbed during soaking. A heat treatment step of passing the impregnated and dried fibers into a second heating zone at high temperature is then required to melt the polymer to adhere, disperse and coat the fibers.

The main disadvantage of this method is the homogeneity of the deposit which is often imperfect. Another problem related to this process is the high porosity induced by the poor distribution of the polymer within the fibers, which may persist after the heat treatment step, thus causing the appearance of a large number of defects in the material. fibrous prepreg. The preimpregnated fibrous material then needs to be shaped into ribbons for example. The shaping technique can further deteriorate the material and weaken it even more because of the presence of these defects.

FR2973802 discloses a method of manufacturing a composite material based on fibers and a vinyl chloride polymer. The method consists firstly in immersing the fibers in a hydrosol bath consisting of an aqueous dispersion of polyvinyl chloride. The impregnated fibers are then dried to remove water, and the hydrosol is gelled to pass from a heterogeneous phase to a homogeneous phase, under the action of heat. This document does not disclose impregnating a plurality of parallel fiber rovings simultaneously in an aqueous dispersion and forming them in unidirectional parallel ribbons by means of a multi-groove heating calender.

WO2008 / 051756 describes meanwhile an aqueous dispersion of thermoplastic polymer powder used to impregnate strands of fibers. Once impregnated the fibers are dried to remove the water and then they are transformed into granules or flakes. This document also does not disclose impregnating a plurality of simultaneous fiber strands simultaneously in an aqueous dispersion and forming them in unidirectional parallel ribbons by means of a multi-groove heating calender.

Regarding the shaping of pre-impregnated fibrous materials in the form of calibrated ribbons, suitable for the manufacture of composite parts three-dimensional automatic removal by means of a robot, it is usually performed in post-processing.

The quality of the pre-impregnated fibrous material ribbons, and therefore the quality of the final composite material, depends not only on the homogeneity of the impregnation of the fibers and therefore the control and reproducibility of the porosity of the fibrous material. pre-impregnated, but also the size and more particularly the width and thickness of the ribbons. Regularity and control of these two dimensional parameters make it possible to improve the mechanical strength of the materials.

Currently, whatever the process used for the impregnation of fibrous materials, the manufacture of ribbons of small width, that is to say of width less than 100mm, generally requires a slitting (that is to say -describe a cut) of strips of width greater than 500 mm, also called tablecloths. The ribbons thus dimensioned are then taken back to be deposited by a robot using a head.

In addition, the rolls of webs not exceeding a length of about 1 km, the ribbons obtained after cutting are generally not long enough to make some large size materials during removal by robot. The ribbons must therefore be roped to obtain a longer length, creating extra thicknesses. These extra thicknesses lead to the appearance of heterogeneities that are detrimental to obtaining good quality composite materials.

Current techniques for impregnating fibrous materials and shaping such fibrous pre-impregnated materials in the form of calibrated ribbons therefore have several disadvantages. For example, it is difficult to homogeneously heat a molten mixture of thermoplastic polymers in a die and at the die outlet to the core of the material, which alters the quality of the impregnation. In addition, the difference in temperature existing between the fibers and a molten mixture of polymers at the level of the impregnation die also alters the quality and homogeneity of the impregnation. The use of organic solvents generally involves the appearance of defects in the material as well as environmental and safety risks. The shaping, by high temperature post-treatment of the pre-impregnated fibrous material in the form of strips, remains difficult because it does not always allow a homogeneous distribution of the polymer within the fibers which leads to obtaining a lower quality material. The splitting of webs for obtaining calibrated ribbons and the splicing of these ribbons induces an additional cost of manufacture. Slitting also generates significant dust problems that pollute the ribbons of pre-impregnated fibrous materials used for robot removal and can cause malfunctions of robots and / or imperfections on the composites. This potentially leads to robot repair costs, a shutdown of production and the scrapping of non-compliant products. Finally, during the slitting step, a not insignificant amount of fibers is deteriorated, inducing a loss of properties, and in particular a reduction of the mechanical strength and the conductivity, ribbons of preimpregnated fibrous material.

[Technical problem]

The invention therefore aims to remedy at least one of the disadvantages of the prior art. The invention aims in particular to provide a method of manufacturing a preimpregnated fibrous material, combining an impregnation technique and a continuous shaping technique, in order to avoid any post-treatment step of the fibrous material, and obtaining a preimpregnated fibrous material having homogeneous fiber impregnation and controlled dimensions with controlled and reproducible porosity upon which the performance of the final composite part depends.

[Brief description of the invention]

For this purpose, the subject of the invention is a method for manufacturing a preimpregnated fibrous material comprising a fiber material made of continuous fibers and a thermoplastic polymer matrix, characterized in that said preimpregnated fibrous material is made of a single unidirectional ribbon or a plurality of unidirectional parallel ribbons and in that said method comprises the following steps: i. a step of impregnating said fibrous material in the form of a wick or several parallel locks, said impregnation step comprising:

iia) immersing said fibrous material in a bath containing an aqueous dispersion of said thermoplastic polymer, said immersion being followed by ib) drying said fibrous material, then

ii. a step of shaping said wick or said parallel strands of said fibrous material impregnated according to step i), by calendering by means of at least one heating radiator in the form of a single unidirectional ribbon or a plurality of unidirectional parallel ribbons; with, in the latter case, said heating calender comprising a plurality of calendering grooves, preferably up to 200 calendering grooves, in accordance with the number of said ribbons and with a pressure and / or spacing between the rolls of said calender regulated by a slave system.

Thus, the hot calendering of the pre-impregnated bit (s), just downstream of the continuous impregnation device, by immersion in a bath containing an aqueous polymer dispersion, makes it possible to homogenize the distribution of the polymer and impregnating the fibers, controlling and reducing the rate of porosity within the preimpregnated fibrous material, and obtaining one or more strips of great length and width and thickness calibrated. The process according to the invention thus makes it possible to avoid the use of molten polymer, of excessive viscosity, the detrimental use of organic solvents, and it also makes it possible to form ribbons of calibrated dimensions without resorting to a step slitting and splicing.

According to other optional features of the method:

it furthermore comprises a step iii) of winding said ribbon or said ribbons onto one or more coils, the number of coils being identical to the number of ribbons, one coil being assigned to each ribbon,

said impregnation step i) is completed by a step of covering said single wick or said plurality of parallel strands after the immersion steps ia) and drying ib) with a molten thermoplastic polymer, which may be the same or different from said thermoplastic polymer of said aqueous dispersion, said covering step being carried out before said calendering step ii), said molten polymer preferably being of the same nature as said polymer of said aqueous dispersion, preferably with said covering being effected by extrusion at right angles to said single wick or to said plurality of parallel rovings, said polymer of said aqueous dispersion is a thermoplastic polymer or a mixture of thermoplastic polymers,

said thermoplastic polymer or thermoplastic polymer blend further comprises carbonaceous fillers, in particular carbon black or carbon nanofillers, preferably chosen from carbon nanofillers, in particular graphenes and / or carbon nanotubes and / or nanofibrils carbon or their mixtures,

the thermoplastic polymer or thermoplastic polymer blend further comprises liquid crystal polymers or cyclized poly (butylene terephthalate), or mixtures thereof, as an additive,

said polymer, or mixture of thermoplastic polymers, is selected from amorphous polymers whose glass transition temperature is such that Tg> 80 ° C and / or from semi-crystalline polymers whose melting point T f is> 150 ° C,

the thermoplastic polymer or thermoplastic polymer mixture is selected from: polyaryl ether ketones (PAEK), in particular poly (ether ether ketone) (PEEK); polyaryl ether ketone ketone (PAEKK), in particular poly (ether ketone ketone) (PEKK); aromatic polyetherimides (PEI); polyaryl sulfones, in particular polyphenylene sulfones (PPSU); polyarylsulfides, in particular polyphenylene sulfides (PPS); polyamides (PA), in particular aromatic polyamides optionally modified by urea units; polyacrylates, in particular polymethyl methacrylate (PMMA); or fluoropolymers, in particular polyvinylidene fluoride (PVDF); and their mixtures,

said fibrous material comprises continuous fibers selected from carbon, glass, silicon carbide, basalt, silica fibers, natural fibers, in particular flax or hemp, sisal, silk, or cellulosic fibers, in particular viscose, or thermoplastic fibers having a glass transition temperature Tg greater than the Tg of said polymer or said polymer mixture when it is amorphous or has a melting temperature Tf greater than the Tf of said polymer or said polymer mixture when the latter is semi-crystalline, or a mixture of two or a plurality of said fibers, preferably a mixture of carbon fibers, glass or silicon carbide, in particular carbon fibers,

the volume ratio of said polymer or mixture of polymers relative to said fibrous material varies from 40 to 250%, preferably from 45 to 125% and more preferably from 45 to 80%,

the volume ratio of said polymer or said polymer mixture with respect to said fibrous material varies from 0.2 to 15%, preferably from 0.2 to 10% and more preferably from 0.2 to 5%;

the calendering step ii) is carried out by means of a plurality of heating calenders,

said heating calender (s) of step ii) comprises (include) an induction or microwave integrated heating system, preferably a microwave, coupled with the presence of carbonaceous charges in said thermoplastic polymer or a mixture of thermoplastic polymers,

said heating calender (s) of step ii) is (are) coupled to a rapid complementary heating device, located before and / or after said (each) calender, in particular a microwave heating device or induction coupled to the presence of carbonaceous fillers in said polymer or said polymer mixture, or IR infrared heater, or Laser or by direct contact with another heat source such as a flame.

The invention also relates to a unidirectional tape of preimpregnated fibrous material, in particular ribbon wound on a reel, characterized in that it is obtained by a method as defined above.

According to an optional feature, the ribbon has a width and a thickness adapted for robot removal in the manufacture of parts in three dimensions, without the need for splitting, and preferably has a width of at least 5 mm and can go up to 100mm, preferably from 5 to 50mm and even more preferably from 5 to 10mm.

The invention also relates to a use of the method as defined above for the manufacture of calibrated ribbons adapted to the manufacture of parts. three-dimensional composites by automatically depositing said ribbons by means of a robot.

The invention further relates to a use of the tape as defined above in the manufacture of composite parts in three dimensions. Said manufacture of said composite parts relates to the fields of transport, in particular automobile, civil or military aeronautics, nautical, railway; renewable energy, in particular wind turbine, tidal turbine, energy storage devices, solar panels; thermal protection panels; sports and recreation, health and medical, ballistics with weapon or missile parts, security and electronics.

The invention also relates to a three-dimensional composite part, characterized in that it results from the use of at least one unidirectional tape of preimpregnated fibrous material as defined above.

The invention finally relates to an implementation unit of the manufacturing method as defined above, said unit being characterized in that it comprises:

a) a continuous impregnation device comprising

a1) an immersion tank containing said aqueous dispersion of said polymer, and a2) a device for drying said single wick or said plurality of parallel wicks,

b) a device for continuously calendering said wick or said parallel wicks, with shaping, in the form of a single ribbon or in the form of several unidirectional parallel ribbons, comprising:

b1) at least one heating radiator, in particular several series of heating radiators, said radiator having a calendering groove or several calendering grooves, and preferably in the latter case having up to 200 calendering grooves,

b2) a system for regulating the pressure and / or spacing between calendering rollers.

[0032] According to other optional features of the unit:

it furthermore comprises a device for winding the ribbons of preimpregnated fibrous material, comprising a number of coils identical to the number of ribbons, a spool being assigned to each ribbon, - said impregnating device a) further comprises and following said immersion tank device a1), and said drying device a2), a device a3) covering said single wick or said plurality of parallel wicks impregnated and dried, by a molten polymer, preferably said covering device a3) comprising an extrusion device at right angles to said single wick or with respect to said parallel locks,

said heating calender (s) comprises (include) an integrated induction heating system,

said heating calender (s) is (are) coupled to a complementary rapid heating device located before and / or after said (each) calender, said heating system being chosen from a device in microwave or induction, particularly when coupled to the presence of carbonaceous charges, or an IR heating system, laser or other device allowing direct contact with the heat source, such as a flame device,

said drying device, situated at the outlet of said immersion tank, is a heating device chosen from a microwave or induction device, in particular when it is coupled with the presence of carbonaceous charges, or a heating system infrared IR, or steam extraction oven.

Other features and advantages of the invention will become apparent on reading the description given by way of illustrative and nonlimiting example, with reference to the appended figures, which represent:

FIG. 1, a diagram of an implementation unit of the process for manufacturing a preimpregnated fibrous material according to the invention,

• Figure 2, a sectional diagram of two rollers constituting a calender as used in the unit of Figure 1.

[Detailed description of the invention]

The term "aqueous dispersion" as used refers to any polymer dispersion in an aqueous medium, comprising emulsion, suspension, including micro-suspension, of polymer powder (s) or dispersion of particles of polymer formed in situ during polymerization in an aqueous medium, for example by emulsion or suspension polymerization.

Polymer matrix

Thermoplastic means, or thermoplastic polymer, a generally solid material at room temperature, which may be crystalline, semi-crystalline or amorphous, and which softens during an increase in temperature, particularly after passing its temperature. glass transition (Tg) if it is amorphous and flows at a higher temperature and can observe a frank fusion at the passage of its so-called melting temperature (Tf) (when it is crystalline or semi-crystalline), and which becomes again solid when the temperature falls below its melting temperature and below its glass transition temperature.

Regarding the polymer constituting the impregnating matrix of the fibrous material, it is preferably a thermoplastic polymer or a mixture of thermoplastic polymers. This polymer or mixture of thermoplastic polymers is crushed in powder form so that it can be used in an aqueous dispersion. The powder particles have an average diameter of preferably less than 125 μm, in order to penetrate the fiber locks.

Optionally, the thermoplastic polymer or thermoplastic polymer blend further comprises carbonaceous fillers, in particular carbon black or carbon nanofillers, preferably chosen from carbon nanofillers, in particular graphenes and / or nanotubes. of carbon and / or carbon nanofibrils or mixtures thereof. These charges make it possible to conduct electricity and heat, and consequently make it possible to improve the lubrication of the polymer matrix when it is heated.

According to another variant, the thermoplastic polymer or thermoplastic polymer blend may further comprise additives, such as liquid crystal polymers or cyclized poly (butylene terephthalate), or mixtures containing them, such as commercialized CBT100 resin. by CYCLICS CORPORATION. These additives make it possible in particular to fluidify the polymer matrix in the molten state, for better penetration into the core of the fibers. Depending on the nature of the polymer, or mixture of thermoplastic polymers used to make the impregnation matrix, in particular its melting temperature, one or other of these additives will be chosen. Advantageously, the thermoplastic polymer or thermoplastic polymer mixture is selected from amorphous polymers whose glass transition temperature is such that Tg> 80 ° C and / or from semi-crystalline polymers whose melting temperature Tf is> 150 ° C.

More particularly, the thermoplastic polymers used in the constitution of the impregnating matrix of the fibrous material may be chosen from:

polymers and copolymers of the family of polyamides (PA), such as high-density polyamide, polyamide 6 (PA-6), polyamide 11 (PA-11), polyamide 12 (PA-12) , polyamide 6.6 (PA-6.6), polyamide 4.6 (PA-4.6), polyamide 6.10 (PA-6.10), polyamide 6.12 (PA-6.12), aromatic polyamides, optionally modified with urea units, in particular polyphthalamides and aramid, and block copolymers, especially polyamide / polyether,

polyureas, in particular aromatic,

polymers and copolymers of the family of acrylics, such as polyacrylates, and more particularly polymethyl methacrylate (PMMA) or its derivatives,

polymers and copolymers of the polyaryletherketone (PAEK) family, such as polyetheretherketone (PEEK), or polyaryletherketone ketones (PAEKK) such as polyetherketone ketone (PEKK) or their derivatives,

aromatic polyether-imides (PEI),

polyarylsulfides, in particular polyphenylene sulfides (PPS),

polyarylsulphones, in particular polyphenylene sulphones (PPSU),

polyolefins, in particular polypropylene (PP);

polylactic acid (PLA),

polyvinyl alcohol (PVA),

fluorinated polymers, in particular polyvinylidene fluoride (PVDF), or polytetrafluoroethylene (PTFE) or polychlorotrifluoroethylene (PCTFE),

- and their mixtures.

[0041] Preferably, the polymers constituting the matrix are chosen from thermoplastic polymers having a melting temperature Tf high, namely from 150 ° C and above, such as polyamides (PA), in particular aromatic polyamides optionally modified with urea units, and their copolymers, polymethyl methacrylate (PPMA) and its copolymers, polyetherimides (PEI), polyphenylene sulfide (PPS), polyphenylene sulfone (PPSU), polyetherketoneketone (PEKK), polyetheretherketone (PEEK), fluoropolymers such as polyvinylidene fluoride ( PVDF).

For the fluoropolymers, it is possible to use a homopolymer of vinylidene fluoride (VDF of formula CH ₂ = CF ₂ ) or a copolymer of VDF comprising by weight at least 50% by weight of VDF and at least one other copolymerizable monomer. with the VDF. The VDF content must be greater than 80% by weight, or even better 90% by weight, to ensure good mechanical strength to the structural part, especially when subjected to thermal stresses. The comonomer may be a fluorinated monomer such as, for example, vinyl fluoride.

For structural parts to withstand high temperatures, in addition to the fluorinated polymers, PAEK (PolyArylEtherKetone) such as polyether ketones PEK, poly (ether ether ketone) PEEK, polyethylene are advantageously used according to the invention. (ether ketone ketone) PEKK, Poly (ether ketone ether ketone ketone) PEKEKK etc.

Fibrous material:

As regards the fibers of constitution of the fibrous material, they are in particular fibers of mineral, organic or vegetable origin. Among the fibers of mineral origin, mention may be made of carbon fibers, glass fibers, basalt fibers, silica fibers, or silicon carbide fibers, for example. Among the fibers of organic origin, mention may be made of thermoplastic or thermosetting polymer-based fibers, such as aromatic polyamide fibers, aramid fibers or polyolefin fibers, for example. Preferably, they are based on thermoplastic polymer and have a glass transition temperature Tg greater than the Tg of the polymer or thermoplastic polymer mixture of constitution of the impregnation matrix when the latter is amorphous, or a melting temperature Tf greater than the Tf of the polymer or thermoplastic polymer mixture of constitution of the impregnation matrix when it is semi-crystalline. Thus, there is no risk of fusion for the organic fibers constituting the fibrous material. Among the original fibers plant, include natural fibers based on flax, hemp, silk including spider, sisal, and other cellulosic fibers, especially viscose. These plant-based fibers can be used pure, treated or coated with a coating layer, in order to facilitate the adhesion and impregnation of the thermoplastic polymer matrix.

These fibers of constitution can be used alone or in mixtures. Thus, organic fibers may be mixed with the mineral fibers to be impregnated with thermoplastic polymer and form the preimpregnated fibrous material.

The fibers are optionally single-strand, multi-strand or a mixture of both, and may have several grammages. They can also have several geometries. Thus, they may be in the form of short fibers, which then make up the felt or nonwovens which may be in the form of strips, sheets, braids, locks or pieces, or in the form of continuous fibers, which make up the 2D fabrics. , fibers or strands of unidirectional fibers (UD) or nonwoven fibers. The fibers constituting the fibrous material may also be in the form of a mixture of these reinforcing fibers of different geometries. Preferably, the fibers are continuous.

Preferably the fibrous material is constituted by continuous fibers of carbon, glass or silicon carbide or their mixture, in particular carbon fibers. It is used in the form of a lock or several locks.

According to the volume ratio of polymer relative to the fibrous material, it is possible to produce so-called pre-impregnated materials "ready to use" or so-called "dry" preimpregnated materials.

In pre-impregnated materials known as "ready to use", the polymer or mixture of thermoplastic impregnating polymers is distributed uniformly and homogeneously around the fibers. In this type of material, the thermoplastic impregnating polymer must be distributed as homogeneously as possible within the fibers in order to obtain a minimum of porosities, ie voids between the fibers. Indeed, the presence of porosities in this type of material can act as points of concentration of stress, during a mechanical tensile stress for example, and which then form fracture initiation points of the pre fibrous material. -impregnated and weakened mechanically. A homogeneous distribution of the polymer or polymer mixture thus improves the mechanical strength and homogeneity of the composite material formed from these preimpregnated fibrous materials.

Thus, in the case of pre-impregnated materials known as "ready to use", the volume ratio of the polymer or mixture of thermoplastic polymers with respect to the fibrous material varies from 40 to 250%, preferably from 45 to 125%, and more preferably 45 to 80%.

The so-called "dry" preimpregnated fibrous materials, in turn, comprise porosities between the fibers and a smaller amount of thermoplastic impregnating polymer which covers the surface fibers to hold them together. These "dry" prepreg materials are suitable for the manufacture of preforms for composite materials. These preforms can then be used to make the infusion of thermoplastic resin or thermosetting resin for example. In this case, the porosities make it possible to facilitate the subsequent transport of the infused polymer resin within the preimpregnated fibrous material, in order to improve the final properties of the composite material and in particular its mechanical cohesion. In this case, the presence of the thermoplastic impregnating polymer on the so-called "dry" preimpregnated fibrous material makes it possible to make the infusion resin compatible.

Thus, in the case of so-called "dry" preimpregnated materials, the volume ratio of the polymer or the mixture of polymers relative to the fibrous material advantageously varies from 0.2 to 15%, preferably from 0.2 to and 10% and more preferably 0.2 and 5%. In this case we speak of polymer web, low weight, deposited on the fibrous material to hold the fibers together.

The method for manufacturing a fibrous material according to the invention advantageously comprises two steps: a first step of impregnating the fibrous material with the thermoplastic polymer, and then a step of shaping the fibrous material pre-impregnated in the form of one or more unidirectional ribbons whose width and thickness are calibrated.

Impregnation stage:

The manufacturing method and the implementation unit of this method are described below, with reference to Figure 1 which schematizes, in a very simplified manner, the constituent elements of this unit 100. Advantageously, the impregnation step of the fibrous material is carried out by passing one or more wicks in a continuous impregnation device, comprising a dip tank 20 containing an aqueous dispersion of polymer ( s) (for example polymer powder (s)) thermoplastic (s). Said dispersion preferably has an average particle size of between 0.3 and 125 μηη.

Each wick to be impregnated is then unwound from a device 10 with reels 1 1 under the traction generated by cylinders (not shown). Preferably, the device 10 comprises a plurality of reels 1 1, each reel for unwinding a wick to impregnate. Thus, it is possible to impregnate several strands of fibers simultaneously. Each reel 11 is provided with a brake (not shown) so as to apply tension to each fiber strand. In this case, an alignment module 12 allows to arrange the fiber locks parallel to each other. In this way the fiber locks can not be in contact with each other, which makes it possible to avoid mechanical degradation of the fibers in particular.

The fiber lock or the parallel fiber locks then pass into the immersion tank 20 containing the aqueous polymer dispersion. The polymer powder (s) is mixed with water to form this dispersion. The strand or strands are circulated in the bath formed by this aqueous dispersion 22. The average diameter of the polymer particles, including in the form of a powder dispersion, in the aqueous dispersion is preferably less than 125 μm, in order to be able to penetrate the fiber lock or strands. Preferably, the particle diameter is between 0.3μηη and 1 μιτι, preferably between 0.4 μιτι and Ι ΟΟμιτι. The pre-impregnated bit (s) then emerge from the tank (20) and move towards a drying device (25) in order to evaporate the water. This drying device 25, situated at the outlet of the immersion tank 20, is advantageously constituted by a heating device chosen from a microwave device or by induction, in particular when it is coupled with the presence of carbonaceous charges, or an infrared heating system IR, or steam extraction oven. Advantageously, when the polymer or polymer mixture comprises carbonaceous fillers, such as carbon black or carbon nanofillers, preferably chosen from carbon nanofillers, in particular graphenes and / or nanotubes. of carbon and / or carbon nanofibrils or mixtures thereof, the effect of induction heating or microwave heating is amplified by the presence of these charges which then lead the heat to the heart of the material.

Optionally, this impregnation step may be completed by a step of covering the wick or pre-impregnated wicks, just at the outlet of the impregnating tank 20 and the drying device 25, and just before the shaping step by calendering. For this purpose, a covering device 30, preferably by extrusion at the angle head, makes it possible to cover the pre-impregnated fiber lock or strands with a molten thermoplastic polymer. The covering polymer may be the same or different from the polymer powder in aqueous dispersion. Preferably, it is of the same nature. Such an overlay makes it possible not only to complete the fiber impregnation step to obtain a final polymer volume content in the desired range, in particular to obtain good quality "ready-to-use" fiber materials, but it also makes it possible to improve the performance of the composite material obtained.

Step of formatting

As soon as (their) exit from the drying device 25, the wick (the parallel locks) pre-impregnated (s), possibly covered (s) with a molten polymer, is (are) put (s) in form in the form of a single unidirectional ribbon or a plurality of parallel unidirectional ribbons, by means of a continuous calender device comprising one or more heating calandres.

So far hot calendering could not be envisaged for a shaping step but only for a finishing step because it did not allow heating at sufficient temperatures, especially when the polymer, or mixture of thermoplastic polymers, impregnation comprises polymers with a high melting temperature.

Advantageously, the heating calenders of the calendering device are coupled to rapid heating means that heat the material not only at the surface but also at the core. The mechanical stress of the calenders coupled to these rapid heating means makes it possible to eliminate the presence of porosities and to homogeneously distribute the polymer, especially when the fibrous material is a so-called "ready-to-use" material. Advantageously this hot calendering not only allows the impregnating polymer to be heated so that it penetrates, adheres and uniformly covers the fibers, but also to control the thickness and the width of the strip or ribbons. fibrous material prepreg.

To be able to make a plurality of unidirectional parallel ribbons, that is to say as many ribbons as pre-impregnated parallel strands, passed in the aqueous dispersion bath 22, the heating calenders, referenced 51, 52, 53 in the diagram of Figure 1, advantageously comprise a plurality of calendering grooves, in accordance with the number of ribbons. This number of grooves can for example go up to 200. A SYST slave system also allows to regulate the pressure and / or spacing E between the rollers 71, 75 of the calender 70, so as to control the thickness ep ribbons. Such a shell 70 is shown schematically in Figure 2 described below.

The calendering device comprises at least one heating radiator 51. Preferably, it comprises several heating radiators 51, 52, 53 connected in series. The fact of having several calender in series makes it possible to pack the porosities in the material and to reduce their rate. This plurality of calenders is therefore important when it is desired to produce so-called "ready-to-use" fibrous materials. On the other hand, to manufacture so-called "dry" fibrous materials it is possible to be satisfied with a lower number of calenders or even a single calender.

Advantageously, each calender of the calendering device has an induction heating system or by microwave, preferably by microwave, in order to heat the polymer or mixture of thermoplastic polymers. Advantageously, when the polymer or mixture of polymers comprises carbon-containing fillers, such as carbon black or carbon nanofillers, preferably chosen from carbon nanofillers, in particular graphenes and / or carbon nanotubes and / or carbon nanofibrils or their mixtures, the effect of heating by induction or by microwaves is amplified by the presence of these charges which then lead the heat to the heart of the material.

Advantageously, each calender 51, 52, 53 of the device is coupled to a rapid heating device 41, 42, 43, located before and / or after each calender, in order to quickly transmit thermal energy to the material. and of perfect impregnation of the fibers with said molten polymer. The rapid heating device may for example be chosen from the following devices: a microwave or induction device, an IR or laser infrared device or other device allowing direct contact with the heat source such as a flame device. A microwave or induction device is very advantageous, in particular when it is coupled to the presence of carbon nanofillers in the polymer or polymer mixture since the carbon nanofillers amplify the heating effect and transmit it to the core of the material.

According to an alternative embodiment, it is also possible to combine several of these heating devices.

The method may further comprise a step of heating the wicks of the fibers, before said impregnation with, as a preferred heating means, heating by microwaves as for the heating system of said heating calender.

Optionally, a subsequent step is to wind the tape or pre-impregnated and shaped tapes. For this, the unit 100 for implementing the method comprises a winding device 60 comprising as many coils 61 as ribbons, a coil 61 being assigned to each ribbon. A splitter 62 is generally provided to deflect the pre-impregnated ribbons to their respective coils 61, while preventing the ribbons touching to avoid any degradation.

Figure 2 shows schematically the detail of the grooves 73 of a calender 70 sectional view. A calender 70 comprises an upper roller 71 and a lower roller 75. One of the rollers, for example the upper roller 71, comprises a crenellated portion 72, while the other roller, i.e., the lower roller 75 in the example comprises a grooved portion 76, the shape of the grooves being complementary to the shape of the protruding portions 72 of the upper roller. The distance E between the rollers 71, 75 and / or the pressure exerted by the two rollers against each other makes it possible to define the dimensions of the grooves 73, and in particular their thickness ep and width I. Each groove 73 is provided to house a bit of fiber which is then pressed and heated between the rollers. The wicks then turn into parallel unidirectional ribbons whose thickness and width are calibrated by the grooves 73 of the calenders. Each calender advantageously comprises a plurality of grooves, the number of which can be up to 200, so as to produce as many ribbons that there are gorges and pre-impregnated locks. The calendering device further comprises a central device, referenced SYST in FIG. 1, controlled by a computer program provided for this purpose, which makes it possible to simultaneously regulate the pressure and / or the spacing of the calendering rollers of all the calanders 51, 52, 53 of the unit 100.

The ribbon (s) or unidirectional (s) thus manufactured (s) has (s) a width and a thickness suitable for removal by robot in the manufacture of parts in three dimensions, without the need for slitting. The width of the ribbon (s) is advantageously between 5 and 100mm, preferably between 5 and 50mm, and even more preferably between 5 and 10mm.

The process for manufacturing a pre-impregnated fibrous material which has just been described thus makes it possible to produce pre-impregnated fibrous materials with high productivity while permitting homogeneous impregnation of the fibers and the control and reproducibility of the porosity, and thus the control and reproducibility of the performance of the final composite article. The homogeneous impregnation around the fibers and the absence of porosities are ensured by the impregnation step, by immersion in an aqueous polymer dispersion, coupled with the use of a mechanical stress shaping device. - even coupled with rapid heating systems that heat the material surface but also heart. The materials obtained are semi-finished products in the form of ribbons calibrated in thickness and width and which are used for the manufacture of structural parts in three dimensions, in the transport sectors such as automotive, aerospace, nautical , or rail, renewable energy, especially wind turbine, tidal turbine, energy storage devices, solar panels; thermal protection panels; sports and recreation, health and medical; weapons, armament and ballistics (weapon or missile parts); security, by a method that may be tape removal assisted by a robot head for example, and known as AFP method (the acronym "Automatic Fiber Placement").

This method therefore makes it possible to continuously produce ribbons of calibrated dimensions and of great length, so that it avoids slitting and splicing steps that are costly and detrimental to the quality of the composite parts manufactured later. The economics of removing the stage of slitting represents about 30-40% of the total cost of producing a ribbon of preimpregnated fibrous material.

The combination of rapid heating devices with hot calenders facilitates the shaping of ribbons to the desired dimensions and allows to significantly increase the production rate of these ribbons compared to conventional shaping processes. Moreover, this combination makes it possible to densify the material by completely eliminating the porosities in so-called "ready-to-use" fibrous materials.

The rapid heating devices also allow the use of many polymer grades, even the most viscous, which can cover all ranges of mechanical strength desired.

For the specific manufacture of ribbons of so-called "dry" fibrous materials, the impregnation step, by immersion in an aqueous dispersion, makes it possible to obtain a uniformly distributed weight of polymers, with a preferred level of polymer. deposited in the order of 5 to 7 g / m.

The method thus makes it possible to produce calibrated ribbons of preimpregnated fibrous material suitable for the manufacture of composite parts in three dimensions, by automatically depositing said ribbons by means of a robot.

[0078]

Claims

1. A method of manufacturing a preimpregnated fibrous material comprising a continuous fiber fibrous material and a thermoplastic polymer matrix, characterized in that said preimpregnated fibrous material is made of a plurality of unidirectional parallel ribbons and said method includes the following steps:

i) a step of impregnating said fibrous material in the form of several parallel locks, said impregnation step comprising:

iia) immersing said fibrous material in a bath containing an aqueous dispersion (22) of said thermoplastic polymer, said immersion being followed by

ib) drying (25) of said fibrous material, then

ii) a step of shaping said parallel locks of said fibrous material impregnated according to step i), by calendering by means of at least one heating calender (51, 52, 53) in the form of a plurality of unidirectional parallel ribbons; with said heating calender comprising a plurality of calendering grooves (73), preferably up to 200 calendering grooves, in accordance with the number of said ribbons and with a pressure and / or a spacing between the rolls of said calender regulated by a slave system.

2. Method according to claim 1, characterized in that it further comprises a step iii) winding said ribbons on several coils (61), the number of coils being identical to the number of ribbons, a coil being assigned to each ribbon .

3. Method according to claim 1 or 2, characterized in that said impregnation step i) is completed by a step of covering said plurality of parallel locks after the immersion steps ia) and drying ib), with a polymer melted thermoplastic, which may be the same or different said thermoplastic polymer of said aqueous dispersion, said covering step being carried out before said calendering step ii), said molten polymer preferably being of the same nature as said polymer of said aqueous dispersion, preferably with said covering being effected by extrusion ( 30) at the head of square with respect to said plurality of parallel locks.

4. Method according to one of claims 1 to 3, characterized in that said polymer of said aqueous dispersion is a thermoplastic polymer or a mixture of thermoplastic polymers.

5. Method according to claim 4, characterized in that said thermoplastic polymer or mixture of thermoplastic polymers further comprises carbonaceous fillers, in particular carbon black or carbon nanofillers, preferably chosen from carbon nanofillers, in particular graphenes. and / or carbon nanotubes and / or carbon nanofibrils or mixtures thereof.

6. Method according to one of claims 4 or 5, characterized in that the thermoplastic polymer or mixture of thermoplastic polymers further comprises liquid crystal polymers or cyclized poly (butylene terephthalate), or mixtures containing it, as additive .

7. Method according to one of claims 1 to 6, characterized in that said polymer, or mixture of thermoplastic polymers, is selected from amorphous polymers whose glass transition temperature is such that Tg> 80 ° C and / or semi-crystalline polymers whose melting point T f is> 150 ° C.

8. Process according to claim 7, characterized in that the thermoplastic polymer or thermoplastic polymer blend is selected from: polyaryl ether ketones (PAEK), in particular poly (ether ether) ketone) (PEEK); polyaryl ether ketone ketone (PAEKK), in particular poly (ether ketone ketone) (PEKK); aromatic polyetherimides (PEI); polyaryl sulfones, in particular polyphenylene sulfones (PPSU); polyarylsulfides, in particular polyphenylene sulfides (PPS); polyamides (PA), in particular aromatic polyamides optionally modified by urea units; polyacrylates, in particular polymethyl methacrylate (PMMA); or fluoropolymers, in particular polyvinylidene fluoride (PVDF); and their mixtures.

9. Method according to one of claims 1 to 8, characterized in that said fibrous material comprises continuous fibers selected from carbon fibers, glass, silicon carbide, basalt, silica, natural fibers in particular flax or hemp, sisal, silk, or cellulosic, in particular viscose, or thermoplastic fibers with a glass transition temperature Tg greater than the Tg of said polymer or said polymer mixture when the latter is amorphous or with a temperature of melting Tf greater than the Tf of said polymer or said polymer mixture when it is semi-crystalline, or a mixture of two or more of said fibers, preferably a mixture of carbon fibers, glass or silicon carbide, in particular carbon fibers.

10. Method according to one of claims 1 to 9, characterized in that the volume ratio of said polymer or polymer mixture relative to said fibrous material ranges from 40 to 250%, preferably 45 to 125% and more preferably 45 to 125%. at 80%.

1 1. Process according to one of Claims 1 to 9, characterized in that the volume ratio of said polymer or said polymer mixture with respect to said fibrous material varies from 0.2 to 15%, preferably from 0.2 to 10%, and more preferably 0.2 and 5%.

12. Method according to one of claims 1 to 1 1, characterized in that the calendering step ii) is performed by means of a plurality of calenders (51, 52, 53) heating.

13. Method according to one of claims 1 to 12, characterized in that said (said) radiator grille (s) of step ii) comprises (include) an integrated heating system by induction or by microwaves, preferably by microwaves, coupled to the presence of carbonaceous fillers in said thermoplastic polymer or thermoplastic polymer blend.

14. Method according to one of claims 1 to 13, characterized in that said (said) calender heating (s) of step ii) is (are) coupled (s) to a rapid complementary heating device (41, 42, 43), located before and / or after said (each) calender (51, 52, 53), in particular a microwave or induction heating device coupled to the presence of carbonaceous charges in said polymer or in said polymer blend, or IR infrared heater, or Laser or by direct contact with another heat source such as a flame.

15. Unidirectional tape of preimpregnated fibrous material, in particular ribbon wound on a reel, characterized in that it is obtained by a process as defined according to one of claims 1 to 14.

16. Tape according to claim 15, characterized in that it has a width and a thickness suitable for robot removal in the manufacture of parts in three dimensions, without the need for splitting, and preferably at a width of at least 5 mm and up to 100 mm, preferably from 5 to 50 mm and even more preferably from 5 to 10 mm.

17. Use of the method as defined in one of claims 1 to 14 for the manufacture of calibrated ribbons suitable for the manufacture of composite parts in three dimensions by automatic removal of said ribbons by means of a robot.

18. Use of the ribbon of preimpregnated fibrous material, as defined in claim 15 or 16, in the manufacture of three-dimensional composite parts.

19. Use according to claim 18, characterized in that said manufacture of said composite parts relates to the fields of transport, in particular automobile, civil or military aeronautical, nautical, railway; renewable energy, in particular wind turbine, tidal turbine, energy storage devices, solar panels; thermal protection panels; sports and recreation, health and medical, ballistics with weapon or missile parts, security and electronics.

20. Three-dimensional composite part, characterized in that it results from the use of at least one unidirectional tape of preimpregnated fibrous material as defined in claim 15 or 16.

21. Unit (100) for implementing the method as defined in one of Claims 1 to 14, characterized in that it comprises:

a) a continuous impregnation device comprising

a1) an immersion tank (20) comprising said aqueous dispersion (22) of said polymer, and

a2) a drying device (25) of said plurality of parallel locks,

b) a continuous calendering device of said parallel strands, shaped, in the form of several unidirectional parallel ribbons, comprising:

b1) at least one heating radiator (51, 52, 53), in particular several series of heating radiators, said radiator having a plurality of calendering grooves (73), and preferably having up to 200 calendering grooves,

b2) a system for regulating the pressure and / or spacing between rollers (71, 75) of calendering.

22. Unit according to claim 21, characterized in that it further comprises a device (60) for winding ribbons of preimpregnated fibrous material, comprising a number of coils (61) identical to the number of ribbons, a reel being assigned to each ribbon.

23. Unit according to claim 21 or 22, characterized in that said impregnating device a) further comprises and following said immersion tank device (20) a1), and said drying device (25) a2 ), a device a3) covering said plurality of impregnated and dried parallel strands, with a molten polymer, preferably said covering device a3) comprising a device (30) for extrusion at right angles to said parallel strands .

24. Unit according to one of claims 21 to 23, characterized in that said heating (s) calender (s) (51, 52, 53) comprises (include) an integrated induction heating system.

25. Unit according to one of claims 21 to 24, characterized in that said (said) radiator grille (s) (51, 52, 53) is (are) coupled to a supplementary heating device. fast (41, 42, 43), located before and / or after said (each) calender, said heating system being chosen from a microwave or induction device, in particular when it is coupled to the presence of carbonaceous charges, or an IR, Laser or other heating system that allows direct contact with the heat source, such as a flame device.

26. Unit according to one of claims 21 to 25, characterized in that said drying device (25), located at the outlet of said immersion tank (20), is a heating device selected from a microwave device or by induction, in particular when coupled with the presence of carbonaceous charges, or an IR infrared heating system, or by steam extraction furnace.